1. Field of the Invention
This invention relates to a silicone rubber composition, a molding product formed from the composition, an elastic revolution body provided with an elastic member having a surface layer formed from the composition and a fixing device having the elastic revolution body.
2. Related Background Art
In an image-forming apparatus such as an electro-photographic copying machine, carryability, releasability and durability are generally required for a carrier roller which carries a sheet-form transfer material or a recording material such as plain paper along the predetermined route.
Particularly, a fixing device provided with a fixing roller or a press roller which carries the transfer material to the predetermined route while giving heat to the unfixed toner images on the transfer material under pressing and preventing the offset phenomena of the toner in a semi-molten or molten state, requires strict carryability, releasability, wear resistance, fixability and durability. The fixing device of this type has at least a heating means such as a fixing roller and a rotating press roller in contact with the heating means under pressing.
The heating means such as a fixing roller comprises a hollow core cylinder made from such a material as aluminum or iron, and a layer coated on the surface of the hollow core cylinder, the layer being composed of a material having a good releasability such as fluorocarbon resin, for example, polytetrafluoroethylene (PTEF) or tetrafluoroethylene-fluoroalkoxyethylene copolymer (PFA) or silicone rubber.
At the inside of the fixing roller, a heater such as a halogen lamp is provided, when required, to heat the surface of the fixing roller to a specific temperature suitable for the fixation. In many cases, the surface temperature of the fixing roller is continuously controlled to keep a set temperature by a sensor.
At the outer peripheral surface of the fixing roller, a cleaning means for removing the attached toner or paper dusts, or a separation means such as a separation nail for preventing a toner image-carrying material such as a transfer material from coiling around the fixing roller is sometimes provided.
On the other hand, the press roller comprises a core cylinder made from such a material as iron or stainless steel, and an elastic member having a good releasability coated on the surface of the core cylinder, the elastic member being composed of silicone rubber. The press roller presses the heating means such as a fixing roller by a pressing means such as a spring.
The toner image-carrying material having an unfixed toner image on the surface is carried by the heating means such as the fixing roller and the press roller with heating under pressing, as pinched therebetween, thereby, heat-fixing under pressing the unfixed toner image on the surface.
When a positively charged toner is to be fixed in a fixing device, problems in image quality have often been encountered such as offset phenomena of toner and line blurring of toner image, and as to the toner attachment to the surface of the press roller. Particularly in a fixing device without a cleaning means for cleaning the surface of the fixing roller, these problems have been encountered more often.